1. Field of the Invention
This invention relates to a device for bilateral upper extremity training for patients with a paretic upper extremity, and more specifically, to a device providing bilateral upper extremity training that facilitates cortical remodeling, sustained relearning and improvement in functional outcomes in both the paretic and non-paretic upper extremity, as well as, to a method of using the device to accomplish sustained re-learning of motor tasks and improved bimanual motor coordination in individuals with a paretic upper extremity.
2. Background of the Technology
Hemiparesis involving the upper extremity following stroke profoundly impacts the functional performance of stroke survivors. There are an estimated 750,000 strokes each year in the United States alone. Of these, more than 300,000 individuals survive stroke; however, these individuals often survive with resultant significant disability. Only 5% of adults regain full arm function following stroke and 20% regain no functional use at all (see, e.g., Gowland, C., et al., and Antagonist Activity During Voluntary Upper- limb Movement in Patients with Stroke, 72 Physical Therapy 624-633 (1992)). It has been previously reported that little change can be facilitated in upper extremity function after approximately 11 weeks following stroke (Nakayama, H., et al., Recovery of Upper Extremity Function in Stroke Patients: The Copenhagen Study, 75 Archives of Physical Medicine and Rehabilitation 852-857 (1994)). Recent evidence, however, suggests that improvement in functional performance of the upper extremity can be seen in patients beyond 11 weeks post-stroke. Animal studies indicate that both central neural remodeling and functional gains can occur long after injury. For example, monkey models of chronic stroke demonstrated functional recovery, as well as, cortical reorganization after being forced to use their paretic limb (see Nudo, R. J., et al., Reorganization of Movement Representations in Primary Motor Cortex Following Focal Ischemic Infarcts in Adult Squirrel Monkeys, 75 J. Neurophys. 2144-49 (1996); Nudo, R. J., et al., Use-Dependent Alterations of Movement Representations in Primary Motor Cortex of Adult Squirrel Monkeys, 16 J. Neurosc. 785-807 (1996); Nudo, R. J., et al., Neural Substrates for the Effects of Rehabilitative Training on Motor Recovery After Ischemic Infarct, 272 Science 1791-4 (1996)). The expansion of cortical maps corresponds to both the affected and non-affected limbs.
While improvement in functional performance of hemiparetic patients is possible, usage of training devices may increase the improvement. However, most training devices are for aerobic exercise or strength training; they do not allow for flexible training of natural actions used in many activities of daily living. The majority of the devices of the prior art are yoked (connected handles) and driven by muscle building principles rather than motor control/neuroplasticity principles. Such an arrangement allows the stronger upper extremity to “carry” the weaker upper extremity, limiting the stress on and active involvement of the weak arm. Alternatively, other devices of the prior art are designed for unilateral strengthening of the paretic arm while the non-paretic limb is constrained. There is increasing evidence that the “unaffected” limb following unilateral stroke presents with some dysfunction relating to the loss of neurophysiological linkage in the central nervous system. Thus, the devices of the prior art fail to rehabilitate the unaffected limb in concert with the paretic limb, which is essential for many tasks. Bilateral upper extremity training of the present invention has the capability to be an effective training paradigm to promote agonist muscle activity in the paretic limb and to promote a facilitation effect from the non-paretic to the paretic limb. Furthermore, the device and method of the present invention has the capability to result in bilateral relearning and cortical remodeling, which improves both intralimb and interlimb coordination and functional outcome.
The specific effects on motor function and coordination post-stroke in the upper extremity have been previously evaluated in fairly high functioning patients. During reaching and grasping tasks, post stroke subjects presented with segmented movement patterns demonstrated difficulty with interjoint coordination especially involving the shoulder and the elbow. When movement times are increased during these tasks, adaptive patterns of movement can be seen. Although there are conflicting reports in the literature as to the specific causes of these differences, it appears that decreased agonist recruitment and poor sensorimotor control seem to be key factors that limit the ability of subjects to carry out these tasks in a smooth and coordinated fashion. This principle extends to bilateral task specific coordination, as well.
While previous reports suggested that little change can be facilitated in upper extremity (UE) function after approximately 11 weeks following stroke, other reports suggests that improvement in functional performance of the upper extremity can be seen in patients with chronic stroke. For example, it has been demonstrated that improved functional performance can occur in UE functions of chronic stroke patients with forced use of the affected limb and restraint of the unaffected limb (see Ostendorf, C., et al, Effect of Forced Use of the Upper Extremity of a Hemiplegic Patient on the Changes in Function, 61 Phys. Ther. 1022-1028 (1981); Wolf, S., et al., Forced Use of Hemiplegic Extremities to Reverse the Effect of Learned Nonuse among Chronic Stroke and Head Injured Patients, 104 Exp Neuro. 125-132 (1989)). These studies offer promise for the rehabilitation of a stroke survivor, but they involve training of a single limb and are restricted to fairly high functioning patients.
For example, in Taub, E., et al., Technique to Improve Chronic Motor Deficit After Stroke, 74 Archives of Physical Medicine and Rehabilitation 347-354 (1983), patients were excluded if they could not achieve at least 10 degrees of extension at the metacarpophalangeal and interphalangeal joints of the hand and 20 degrees of extension at the wrist of the affected limb. Wolf et al. (1989) required subjects to be able to actively initiate wrist and finger extension on the paretic side. This has restricted the success of the forced use paradigm to the higher functioning patient. Using the present invention, however, a patient with minimal active movement, limited to just the shoulder, demonstrated changes in upper extremity function. Thus, the present invention is capable of being used by patients at all levels of recovery post stroke, providing minimal movement is present.
In addition, many human physical functions involving the upper extremities are bilateral in nature, and, although each limb may not perform the same specific task, there exists a coordination between upper limbs that permits functional efficiency. Therefore, the present invention, a bilateral upper extremity exercise training device, facilitates greater improvement of the paretic upper extremity than a unilateral one.
Finally, as mentioned earlier, evidence shows that the “unaffected” limb following unilateral stroke presents with dysfunction as well. Limitations have been demonstrated in fine and gross motor dexterity, motor coordination, global functional performance, thumb kinesthesia, speed of finger taping and grip strength (Desrosiers, J., et al., Performance of the ‘Unaffected’ Upper Extremity of Elderly Stroke Patients, 27 Stroke 1564-70 (1996); Prigatano, G., et al., Speed of Finger Tapping and Goal Attainment After Unilateral Cerebral Vascular Accident, 78 Archives of Physical Medicine and Rehabilitation 847-852 (1997)). This suggests a potential benefit to both upper extremities with bilateral versus strict unilateral training of the upper extremities post-stroke.
No studies have been done evaluating the effectiveness of an exercise intervention for post-stroke hemiplegia where training involves both upper extremities at the same time. Training in this context may help the neuromuscular system to use the extremities in a more coordinated fashion that will not only improve motor performance of the hemiplegic upper extremity but may impact functional outcomes of both limbs as well. For example, Gauthier, et al. (1994) demonstrated improvement in the muscle activity and torque production of the hemiplegic lower extremity through training that included resistive exercise of the “unaffected” lower extremity. This provides evidence that the use of bilateral training can be an effective training mechanism for the motor performance of the lower extremity. Other studies have also demonstrated functional gains in bilateral training of the lower extremities using a treadmill or walking protocols.
Most currently used rehabilitation therapies require the presence of a therapist; patients can not use such therapies on their own. Alternatively, robotic therapy devices are complex, bulky and expensive. None of the physical therapy or exercise devices currently available disclose a simple, portable, non-motorized, adjustable and independent bilateral limb trainer.